The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Blame shifting over Vic emergency figures

The Commonwealth and Victorian governments are pointing the finger at each other over the slipping performance of the state's emergency rooms.

Figures released on Friday showed Victorian hospitals were unable to meet the benchmark level of treating 70 per cent of emergency room patients within four hours, with the Western Hospital among the worst in the country for its category.

State Health Minister David Davis was quick off the mark to blame the federal government, saying the state had been left $475 million short.

"It is an outrageous bid by the federal government to prop up its own promised budget surplus by ripping money out of Victorian hospitals and away from Victorian patients," he said in a statement.

But Mr Davis' federal counterpart Tanya Plibersek said the Victorian government was making excuses for failing to meet targets, and pointed to state health funding cuts.

"Victoria renegotiated its interim National Emergency Access Targets down from those originally agreed," Ms Plibersek said.

"Despite lowering the bar, Victoria is still struggling to meet its target."

There was a positive side to the figures, with Williamstown Hospital, in Melbourne's west taking the mantle as the highest achiever from any category, with 93 per cent of patients departing emergency within four hours.